1. Field of the Invention
This invention pertains to a cross-infection-prevention medical device. More particularly, it pertains to an infection prevention syringe which has a retractable needle assembly that protects patients and medical workers from disease or injury due to reuse or accidental contact with the needle.
In 1987 the first lawsuit arose as the result of a healthcare worker contracting AIDS on the job. The unfortunate doctor contracted the disease after accidentally sticking herself with a needle after giving an AIDS patient an injection. The patient's blood was on the needle and was transferred to her body via the needlestick injury.
Over 20 different pathogens have been documented as being transferred from patient to healthcare worker by needlestick injuries. Over 12,000 become infected with and nearly 300 workers die annually from hepatitis B contracted on the job..sup.1 Studies have shown that 17 percent of needle-stick injuries occur during use of the syringe, 70 percent occur when the user prepares the device for disposal, and 13 percent occur during or after disposal. Overall, one third of injuries occur during recapping of the device..sup.2 1. Jagger, Janine. Rates of Needle-Stick Injury Caused by Various Devices in a University Hospital. New England Journal of Medicine. Aug. 4, 1988, p. 284. 2. Ibid.
2. Description of Related Art
In many countries, medical workers reuse disposable syringes, even though they know they should not, because of a lack of adequate healthcare supplies. Epidemics have been caused in hospitals by this practice, as patients are contaminated by needles used on other patients. In the majority of cases, it would be better for the patient to receive no medication than for them to receive medication and be infected with a life-threatening disease. Similar problems result from the reuse of syringes by drug abusers.
U.S. Pat. No. 4,710,170 to Haber et al discloses a disposable, anti-needle strike and anti-drug-abuse syringe. The syringe includes a conventional hypodermic needle and luer lock assembly which is connected to and supported from a needle carrier base. The needle carrier base is removably attached to a first end of the syringe cylinder, such that the needle projects outwardly therefrom for injecting a fluid from the cylinder in the conventional manner.
The syringe also includes a piston assembly comprising the detachable connection of an elongated piston stem to a seal and lock assembly. A torroidal seal, formed at one end of the seal and lock assembly, functions as a plunger when the piston assembly is moved axially through the syringe cylinder during a fluid injection procedure. The torroidal seal has a receptacle formed therein at which the seal and lock assembly is adapted to selectively engage the needle carrier base when the piston assembly is moved to the first end of the syringe cylinder. The piston assembly is then moved away from the first cylinder end, whereby to remove the needle carrier base and the attached hypodermic needle from the first to an opposite end of the cylinder. The needle carrier base is anchored at the opposite cylinder end, such that the hypodermic needle extends into and is shielded by the syringe cylinder. The piston stem is detached from the piston assembly by bending the stem relative to the seal and lock assembly. The piston stem is then inserted through an orifice at the first end of the syringe cylinder from which the needle carrier base was previously removed. The stem is axially advanced through the interior of the syringe cylinder towards the opposite end thereof until contact is made with the needle cannula at the interior of the cylinder. The impact of the piston stem against the needle cannula bends, rather than breaks, the needle within the cylinder. The piston stem is locked in its final position within the syringe cylinder to prevent access to or contact with the needle. The syringe may then be discarded in a normal fashion. The resulting cartridge is rendered safe by locking the hypodermic needle and needle carrier base within the syringe cylinder, so that the needle is shielded by the syringe cylinder.
U.S. Pat. No. 4,710,170, the Haber invention, causes waste of medication due to the amount of "dead space" in the design; medication is not completely expelled from the recesses which remain after the plunger has been pushed to the distal end of the syringe. In addition, the Haber invention can be reassembled; the parts can be separated from each other, and the "needle carrier base" can be refixed in place at the end of the syringe permitting reuse of the syringe. Furthermore, the needle assembly is rendered non-reusable only if the user chooses to destroy it, and if the user does choose to do so it will require extra effort and time. The Haber invention necessitates the attaching of a plunger to a separate "seal and lock assembly" before the syringe may be used, a step requiring more assembly and more room for quality problems.
The Hall invention, described in U.S. Pat. No. 4,935,015 requires that the needle be attached to the syringe barrel by being inserted through the proximal opening of the syringe barrel and being screwed into place at the distal end of the syringe. The plunger is used to push the needle up into place through the syringe barrel and to screw it in place. The plunger must then be pulled out of the needle base. This process is time consuming and leaves much opportunity for the needle to be contaminated and for the user to stick him or herself with the unused needle.
The device disclosed by Haining in U.S. Pat. No. 4,790,822 could be broken down and reassembled for reuse. In addition, prior to initial use, the top or the T-type head could be cut off to deactivate the mechanism which makes the syringe non-reusable. In addition, the user must break off the plunger to prevent the needle from accidentally being pushed out of the barrel after use, requiring extra time and effort and potentially causing a jolting movement of the syringe which would lead blood to splatter from the end of the syringe.